Vapor phase production of acrylonitrile



United States Patent No-Drawing. Application May 14,1957 Serial No, 658,950

' ""9"Claims. *(Cl. 260-4653) This invention relatesflto the production of chemicals and in particular to ,an improved process for the productionof acrylonitrile. The application is, in part, a continuation of copending application Serial No. 542,- 474,'filed October 24, 1955.

A principalobject ofthe present invention is to produce high yields of acrylonitrile readily andcheaply -by reacting hydrogen cyanide with acetylene in the vapor phase in the presence of a suitable catalyst.

Otl1er objects of the invention will in part-beobvious and will in part appear hereinafter.

The invention accordingly comprises. the ;process "involving the several steps and the relation andthe order of one or more of 'such steps with respect to ,eachof the others which are exemplified in the following detailed disclosure, and the scope .of the application of which willbe indicated in theclaims.

For a fuller understanding of the nature and objectsof the invention, reference should be had to thefollowing detailed description. I

'The present invention is directedto the v-aporzphase production of acrylonitrile by passing an acetylene stream and hydrogen cyanide over a suitable-catalyst for reaction at an elevated temperature. :As is known, there is a large temperature rise due to the heat release of this reaction. If all of the reactants are fed preheated into the inlet of .a' single reactor and are used up inthe reaction, the temperature of thereaction gases is toofihigh and causes a significant decrease in the conversion -to acrylonitrile due to deleterious side reactions. Although in actual practice complete conversion of the reactants is not achieved, the temperature rise which-occurs is such as to cause control difficulty.

In one embodimentof .the :present invention, better temperature control is achieved by introducing or injecting hydrogen cyanide oracetylene or mixtures ot'the reactants into the reactor at temperature of the substance injectedis significantly below the reaction temperatures so astobbtain a better reaction and temperature control. This injection cools the rection gases at the cross section ofthe-injection point. By suitable proportioning of the feed gases and injection of cool reactants, it is possible to maintain the reaction at the most desirable temperature levels --for maximum conversions and yields.

In another embodiment of the inventiomthe acetylene stream utilized is a dilute acetylene stream which .contains less than about 15 percent acetylene. The preferred acetylene streams can be obtained by diluting pure acetylene with diluents such as nitrogen, hydrogen, carbon oxides, mixtures-thereof and the like. Acetaylene streams containing'lessthan-about IS -percent acetylene are produced directly by such well-known methods as the Wulfi, and Sachsse processes and like processes which utilize hydrocarbons or mixtures 'thereof as the starting .materials.

One well-known method I for producing acetylene streams containing less than about 15 percent acetylene .50 one or-more points. The

. drocarbons.

' internal diameter of the reactor. 7 'deoxygenated porous charcoal support impregnated with velocity of about about 635 -C. developed about jot the 'bed-was' sufficient to 'internal diameter of three 'side ports spaced 38.0, 53.5 and 69 inches respectively from the top of the reactor. of a deoxygenated porous through the three side 2,847,449 Patented Aug. 12, 1958 ice 2,236,534, 2,236,535, 2,236,555,2,319,679,- 2,475,093and many others.

Another well-known method for producing dilute acetylene is the Sachsse process. This Fprocess 1nv-olves the incomplete combustion of a hydrocarbon-or mixtures of hydrocarbons to form acetylene stream eontainin'g less than about 15 percent acetylene. ,A more detailed discussion of the Sachsse process maybe found in U. S. Patents 2,195,227,-2,235,749,-and- 2,664,450.

The composition of the dilute acetylene streams obtained fromtheabove processes depends, to -a great'extent, upon the hydrocarbon or hydrocarbonsemployed as the starting material. However, these streams Liganerally contain various proportions of 'acetylene (in amounts of less than about 15percent), carbon oxides, hydrogen, nitrogen and unsaturatedrand/or'saturated hy- The reaction between acetylene and hydro- .gen cyanide iscarried out at a temperature within the rangeof tromabout 450 C. to 700C. and-in the presence of'an inert support and preferably a porous carbonaceous-support impregnated with from about-'3fpercent to about l5=percent by'weight'of either an alkali metal hydroxide, cyanide or carbonate.

Specific detailed methods of carrying out the present invention are set forth in the following non-limiting examples.

Example I An aluminized reactor '76 inches ,in length with an three inches wasfittedwith side 6 inch intervals along the length of The reactor co'ntained8'000 grams of a ports spaced at about about-l0 percent by weight of'sodium hydroxide. -A stream of dilute acetylene and hydrogen cyanide was passedthroughthe reactor containingithecatalyst. The reactor was 'maintained'at a temperatureof about 620 C. and the gases passed through the reactorat-a space 580 hr.. (STP). The mole ratio of acetylenetdhydrogen cyanide was 0.8 withjthe amount of acetylene in thefeed stream amounting to-about.. 8

percent. The remainder of the s'tream consisted of hydrogen and nitrogen. During. the run a hot spot .of 16 inches below the-top of the catalyst bed. Admission of 5.5 percent of cold (roo'rntempe'rature) teed gases l3 inches below the'top depress the hot jspot about C. in about 20 minutes. After 59 hours the run' was terminated. The conversion of acetyleneto.acrylonitrile was 67.1 percent based on acetylene whilethe .yieldwas 85.8 percent based on hydrogen cyanide.

Example 11' 96 inches in length .with an inches was provided with three An aluminized reactor The reactor contained 8000 grams charcoal support impregnated with about 10 percent by weight of sodium hydroxide. The feed gases consisting of, a mixture of hydrogen cyanide and a-fdilute acetylene stream containing about 8 percent acetylene wee distributed to the catalyst bed ports, as well' as tothe'top of the reactor. For a periodof 20'-l:1ours,the distribution of feed gases was 50 percent to the top, sc percent to the highesteport line, 3-8'.0 inches 'frornthe top of the reactor, :andEJOp'er'cent e'aeh to the remaining two ports. The reactor was heated to a temperature of about 620 This by heating in the range of 500 C. to 900 C. and passing hydrogen over the heated charcoal until substantially all the removed. The resulting deoxygenated charcoal is impregnated with an alkali metal hydroxide, cyanide or carbonate.

The temperature range in about 450 C. to about 700 may vary from about 100 hr. (STP) to about 1000 hr? (STP), preferred space velocities being on the order of between about 300 and 800 hr. (STP) at reaction temperatures between about 525 C. and 630 C.

The molar ratio of acetylene to hydrogen cyanide may be varied quite widely between about 0.5 :1 to about 1.6 :1 and higher.

ence of other diluents.

In the examples cited above, lene was employed. The above use of a dilute stream of acetyexamples, illustrating the l. A nitrile 4 passing a dilute acetylene stream and hydrogen cyanide over a suitable catalyst for reaction at an elevated temperature. The acetylene is preferably present in an amount which is greater than that stoichiometrically necessary to react with the hydrogen cyanide thereafter there is added to the resulting reaction The mole ratio of acetylene to hydrogen cyanide in the first reaction is maintained under conditions which favor maximum conversion of hydrogen cyanide to acrylonitrile. Thus, it is preferred to employ an amount of acetylene which is in excess of that stoichiornetrically necessary to completely combine or react with the hydrogen cyanide present. The mole ratio of acetylene to hydrogen cyanide in the second reaction is preferably such that the amount of hydrogen cyanide is in excess of that stoichiometrically necessary to react with the remaining acetylene.

If desired, the reaction can be carried out in a single reactor in such a manner as to eflect a two-stage reaction. Also, the reaction can be carried out in more than two stages. In one method of operating, for example, the first temperature rise can be kept to a controllable level stoichiometric amount required to react with the hydrogen cyanide. In order to maintain this preferred ratio, additional quantities of acetylene may also be injected into the reactor at one or more intermediate points.

of from about 10 illustrative and not in a limiting sense.

What is claimed is:

process for the vapor phase production of acrylowhich comprises introducing acetylene and hydrogen cyanide into the inlet of a reactor, said reactor containing an inert support carrying a catalyst selected from the group consisting of the alkali metal hydroxides, carbonates and cyanides and being maintained at a tel.- perature between about 450 C. and 700 C., adding further quantities of at least one reactant maintained at a temperature below 450 C. to the reactor at a plurality of points distributed along the length of the reactor to main tain proper temperature control of the reaction, and recovering the acrylonitrile formed.

2. A process according to claim 1 wherein further quantities of acetylene and hydrogen cyanide are added to the reactor.

3. A process according to claim 1 wherein further quantities of acetylene are added to the reactor.

4. A process according to claim 1 wherein further quantities of hydrogen cyanide are added to the reactor.

5. The process according to claim 1 wherein quantities of dilute acetylene are added to the reactor.

6. A process according to claim 1 wherein the acetylene introduced at the inlet of the reactor and acetylene added to the reactor at a plurality of points distributed along the length of the reactor is a dilute acetylene stream.

7. A process according to claim 6 wherein the dilute acetylene streams contain less than about 15 percent acetylene.

8. A process according to claim 1 wherein further quantities of at least one reactant maintained on the order of about room temperature are added to the reactor.

9. A process for the vapor phase production of acrylonitrile which comprises introducing acetylene and hydrogen cyanide into the inlet of a reactor, said reactor containing an inert support carrying a catalyst selected References Cited in the file of this patent UNITED STATES PATENTS 2,385,551 Spence et a1. Sept. 25, 1945 2,413,623 Harris Dec. 31, 1946 2,419,186 Harris et al Apr. 15, 1947 2,502,678 Sapulding et al. Apr. 4, 1950 OTHER REFERENCES Migrdichian: The Chemistry of Organic Cyanogen Compounds, 1947, page 349. 

1. A PROCESS FOR THE VAPOR PHASE PRODUCTION OF ACRYLONITRILE WHICH COMPRISES INTRODUCING ACETYLENE AND HYDROGEN CYANIDE INTO THE INLET OF A REACTOR, SAID REACTOR CONTAINING AN INERT SUPPORT CARRYING A CATALYST SELECTED FROM THE GROUP CONSISTING OF THE ALKALI METAL HYDROXIDES, CARBONATES AND CYANIDES AND BEING MAINTAINED AT A TEMPERATURE BETWEEN ABOUT 450*C. AND 700*C., ADDING FURTHER QUANTITIES OF AT LEAST ONE REACTANT MAINTAINED AT A TEMPERATURE BELOW 450*C. TO THE REACTOR AT A PLURALITY OF POINTS DISTRIBUTED ALONG THE LENGTH OF THE REACTOR TO MAINTAIN PROPER TEMPERATURE CONTROL OF THE REACTION, AND RECOVERING THE ACRYLONITRILE FORMED. 